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本文用光学显微镜、电子显微镜和 X 射线衍射仪,对60Si2Mn 钢经870℃×20分钟奥氏体化后在320～500℃等温不同时间所获得的组识形态和结构进行了研究。认为这种钢的上贝氏体在等温形成的前期阶段为无碳化物贝氏体或称 BI 型上贝氏体,后期阶段为典型粒状贝氏体。粒状贝氏体的形成是 BI 型上贝氏体中贝氏体铁素体长大与富碳奥氏体为减少界面能而进行球化过程的结果。BI 型上贝氏体中奥氏体量达22%,其含碳量为1.52%,经-78℃处理和300℃以下回火显示了高度的稳定性。此外,初步探讨了 BI 型上贝氏体的机械性能。
In this paper, the morphology and structure of 60Si2Mn steel obtained after isothermal austenitizing at 870 ℃ for 20 minutes at different temperatures from 320 ℃ to 500 ℃ were studied by optical microscope, electron microscope and X-ray diffraction. The upper bainite of this kind of steel is considered to be carbide-free bainite or BI-type upper bainite at the early stage of isothermal formation, and the typical granular bainite at the later stage. The formation of granular bainite is the result of the nodular ferrite growth and the carbon-rich austenite in BI-type upper bainite in order to reduce the interfacial energy. BI type bainite austenite amount of 22%, the carbon content of 1.52%, after -78 ℃ treatment and tempering below 300 ℃ showed a high degree of stability. In addition, the mechanical properties of BI-type upper bainite were discussed preliminarily.